Particle and photoacoustic contrast agent having the particle

Abstract

An iron oxide particle constituting a Resovist (trademark) absorbs a small quantity of light in a near infrared region and emits a weak photoacoustic signal. According to a particle having a catechol-like compound and iron atoms, the particle having a ratio of the number of moles of the catechol-like compound to the number of moles of the iron atoms of 270/10,000 or more, light absorption in the near infrared region increases and a strong photoacoustic signal can be transmitted.

What is claimed is: 
     
       1. A contrast agent for photoacoustic imaging, comprising a particle,
 wherein the particle has dopamine and iron atoms, and 
 wherein the particle has a ratio of a number of moles of the dopamine to a number of moles of the iron atoms that is from 270/10,000 to 3,000/10,000. 
 
     
     
       2. The contrast agent according to  claim 1 , wherein at least part of the iron atoms form a complex with a catechol-like compound. 
     
     
       3. The contrast agent according to  claim 1 , further comprising oxygen atoms, wherein at least part of the iron atoms are bonded to the oxygen atoms. 
     
     
       4. The contrast agent according to  claim 1 , wherein the particle is amorphous. 
     
     
       5. The contrast agent according to  claim 1 , wherein the particle absorbs light in a near infrared region. 
     
     
       6. The contrast agent according to  claim 1 , wherein an average particle size is 1 nm to 5,000 nm. 
     
     
       7. The contrast agent according to  claim 1 , further comprising a dispersion stabilizer. 
     
     
       8. The contrast agent according to  claim 7 , wherein the dispersion stabilizer is selected from the group consisting of a sugar and derivatives thereof. 
     
     
       9. The contrast agent according to  claim 7 , wherein the dispersion stabilizer comprises at least one selected from the group consisting of a dextran, a carboxydextran, an aminated dextran, a pullulan, and a polyethylene glycol. 
     
     
       10. A contrast agent for photoacoustic imaging, comprising a particle,
 wherein the particle has dopamine and iron atoms, and 
 wherein a molar absorption coefficient per iron amount of the particle is 580 or more.